diff --git a/specs/waku/v2/waku-filter.md b/specs/waku/v2/waku-filter.md
index fbee22bd..8bd8bfae 100644
--- a/specs/waku/v2/waku-filter.md
+++ b/specs/waku/v2/waku-filter.md
@@ -83,7 +83,7 @@ message FilterRequest {
   repeated ContentFilter contentFilters = 3;
 
   message ContentFilter {
-    repeated string contentTopics = 1;
+    repeated uint32 contentTopics = 1;
   }
 }
 
diff --git a/specs/waku/v2/waku-message.md b/specs/waku/v2/waku-message.md
index 1d6cef8d..04427004 100644
--- a/specs/waku/v2/waku-message.md
+++ b/specs/waku/v2/waku-message.md
@@ -49,7 +49,7 @@ The `version` field MAY be filled out to allow for various types of payload encr
 ```protobuf
 message WakuMessage {
   optional bytes payload = 1;
-  optional fixed32 contentTopic = 2;
+  optional uint32 contentTopic = 2;
   optional uint32 version = 3;
 }
 ```
diff --git a/specs/waku/v2/waku-rln-relay.md b/specs/waku/v2/waku-rln-relay.md
index 3c6d6d40..554b5f3c 100644
--- a/specs/waku/v2/waku-rln-relay.md
+++ b/specs/waku/v2/waku-rln-relay.md
@@ -120,7 +120,7 @@ TODO: discuss about the economic spam guarantees
 // TODO to reflect this change on WakuMessage spec once the PR gets mature
 message WakuMessage {
   optional bytes payload = 1;
-  optional fixed32 contentTopic = 2;
+  optional uint32 contentTopic = 2;
   optional uint32 version = 3;
   optional ProofBundle proofBundle = 4;
 }